Modular medical pump assembly

ABSTRACT

A medical pump subassembly comprises a magnetic cup forming a recess. The magnetic cup includes a protrusion within the recess. The cup forms a central aperture through the protrusion. The medical pump subassembly further comprises an electromagnetic coil within the recess and circumscribing the protrusion, a weld ring surrounding the recess, a barrier plate covering the recess, and a seal between the weld ring and the barrier plate to fluidically separate an interior of the cup from an external surface of the barrier plate.

This application claims the benefit of U.S. Provisional Application No.61/174,457, filed Apr. 30, 2009, the entire content of which isincorporated by reference herein.

TECHNICAL FIELD

The disclosure relates to medical pumps, and more particularly, butwithout limitation, to implantable medical devices including medicalpumps.

BACKGROUND

Medical pumps can be used to treat a variety of physiological,psychological, and emotional conditions. For some medical conditions,medical pumps can restore an individual to a more healthful conditionand a fuller life. For example, medical pumps may be used for chronicdelivery of therapeutic agents, such as drugs. As one specific example,a medical pump may be used to deliver insulin to a diabetic patient.Other examples include delivery of pain relief medication, e.g., to theintrathecal or epidural space of a patient, to alleviate chronic pain.

Some medical pumps are implantable. Implantable medical pumps may beimplanted at a location in the body of a patient and deliver a fluidmedication through a catheter to a selected delivery site within thebody of a patient. Typically, a catheter connects to a catheterconnection port at the outlet of the medical pump and delivers atherapeutic agent at a programmed infusion rate to a predeterminedlocation to treat a medical condition. An implantable medical pump isimplanted by a clinician into a patient at a location that interferes aslittle as practicable with patient activity. For example, implantablemedical pumps are often implanted subcutaneously in the lower abdomen ofa patient. Implantable medical pumps may include self-sealing fluidreservoirs accessible through ports to facilitate in-service refillingby percutaneous injection.

SUMMARY

In general, the disclosure relates to medical pumps that facilitate sealintegrity testing of a medical pump subassembly prior to the fullassembly of an implantable medical device including the medical pump. Inaddition, the disclosure describes techniques that may facilitatepotting of an electromagnetic coil within a medical pump subassembly,which may speed up the assembly process of a medical pump.

In one example, the disclosure is directed to a medical pump subassemblycomprising a magnetic cup forming a recess. The magnetic cup includes aprotrusion within the recess. The cup forms a central aperture throughthe protrusion. The medical pump subassembly further comprises anelectromagnetic coil within the recess and circumscribing theprotrusion, a weld ring surrounding the recess, a barrier plate coveringthe recess, and a seal between the weld ring and the barrier plate tofluidically separate an interior of the cup from an external surface ofthe barrier plate.

In another example, the disclosure is directed to a medical pumpassembly comprising a magnetic cup forming a recess. The magnetic cupincludes a protrusion within the recess, and the cup forms a centralaperture through the protrusion. The medical pump assembly furthercomprises a one-way valve that control fluid flow within the centralaperture, an electromagnetic coil within the recess and circumscribingthe protrusion, a barrier plate covering the recess, a piston within thecentral aperture and a magnetic pole attached to the piston. Themagnetic pole is adjacent to an external surface of the barrier plate.In addition, the medical pump assembly also comprises a cover enclosingthe magnetic pole between an interior surface of the cover and anexternal surface of the barrier plate, wherein the cover constrains themotion of the piston within the central aperture and a seal between thecup and the barrier plate and the cover to fluidically separate aninterior of the cup from the external surface of the barrier plate.

In another example, the disclosure is directed to a method ofmanufacturing a medical pump comprising placing an electromagnetic coilwithin a recess of a magnetic cup and circumscribing a protrusion in themagnetic cup. The protrusion is within the recess, and the magnetic cupforms a central aperture through the protrusion. The magnetic cup isincluded in a magnetic cup/weld ring assembly also including a weld ringsurrounding the recess. The method further comprises sealing a barrierplate to the weld ring to enclose the electromagnetic coil within therecess to fluidically separate an interior of the cup from an externalsurface of the barrier plate, and potting the electromagnetic coilwithin the recess after sealing the barrier plate to the weld ring tocreate a potted magnetic cup/electromagnetic coil assembly.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram illustrating an example of a fluiddelivery system, which includes an implantable medical device (IMD) witha medical pump that is configured to deliver a therapeutic agent to apatient via a catheter.

FIG. 2 is functional block diagram illustrating an exemplary IMD with amedical pump.

FIGS. 3-6 illustrate components of an exemplary modular medical pumpthat facilitates seal testing of a pump coil subassembly.

FIGS. 7-10 illustrate components of an exemplary modular medical pumpthat facilitates pump operation testing prior to assembling a modularpump in a bulkhead.

FIGS. 11, 12A and 12B illustrate components of an exemplary modularmedical pump that facilitates pump operation testing prior to assemblingthe modular pump in a bulkhead.

FIG. 13 is a flowchart illustrating techniques for manufacturing amedical pump.

FIG. 14 is a flowchart illustrating techniques for manufacturing amedical pump including a pump module.

FIG. 15 is a flowchart illustrating techniques for delivering specifiedquantities of therapeutic fluid to patients using medical pumps withfixed stroke lengths.

FIG. 16 is illustrates components of an exemplary modular medical pumpthat facilitates pump operation testing prior to assembling the modularpump in a bulkhead.

DETAILED DESCRIPTION

Medical devices are useful for treating, managing or otherwisecontrolling various patient conditions or disorders, such as, but notlimited to, pain (e.g., chronic pain, post-operative pain or peripheraland localized pain), tremor, movement disorders (e.g., Parkinson'sdisease), diabetes, epilepsy, neuralgia, chronic migraines, urinary orfecal incontinence, sexual dysfunction, obesity, gastroparesis, mooddisorders, or other disorders. Some medical devices may be configured todeliver one or more therapeutic agents, alone or in combination withother therapies, such as electrical stimulation, to one or more targetsites within a patient. For example, in some cases, a medical pump maydeliver one or more pain-relieving drugs to patients with chronic pain,insulin to a patient with diabetes, or other fluids to patients withdifferent disorders. A medical pump may be implanted in the patient forchronic therapy delivery (e.g., longer than a temporary, trial basis) ortemporary delivery. Example therapeutic agents deliverable with medicalpumps as described herein include, but are not limited to, insulin,morphine, hydromorphone, bupivacaine, clonidine, other analgesics,baclofen and other muscle relaxers and antispastic agents, geneticagents, antibiotics, nutritional fluids, hormones or hormonal drugs,gene therapy drugs, anticoagulants, cardiovascular medications orchemotherapeutics.

A medical pump may be configured to deliver a therapeutic agent from thefluid reservoir to a patient according to a therapy program, which may,for example, specify a delivery rate of a fluid delivered to the patientby the medical pump. As another example, a therapy program may adjustthe delivery rate automatically based on physiological characteristicsof a patient. In some instances, an external controller may be used toalter the therapy program as well as send and receive data relating tothe operation of the medical pump. In different examples, an externalcontroller may be operated by either one or both of a clinician and thepatient.

Drug therapies may dictate a specific target dose resolution in ordermeet therapy efficacy requirements; insulin therapy is one example. Inaccordance with the techniques disclosed herein, fully functional pumpsubassemblies can be built, calibrated and labeled. The calibration mayinclude precisely measuring the fluid volume for a single pump stoke andstoring a representation of that volume in memory for future therapydelivery. In addition, the techniques described herein provide for pumpsubassemblies with customized dosage resolutions, i.e., stroke volumeand drug types (e.g. insulin) that can be “dropped in” (like a carengine) to a common pump framework, such as a bulkhead.

In addition, in accordance with the techniques disclosed herein, fullyfunctional pump subassemblies may greatly reduce development cycle time,manufacturing cost, scrap, and piece part costs since the pumpsubassemblies can be built on a feeder line and functionally tested asstandalone components prior to being integrated into the pump framework.Further aspects of this disclosure include pump subassemblies designswith welding features that provide high weld yields, i.e., a low rate ofdefective welds.

In accordance with the techniques disclosed herein, a fully functionalpump subassembly can include an electromagnetic drive coil,electromagnetic material to drive flux, a reciprocating electromagneticactuator, a piston, a bore, a check valve, a stroke length setter, and abacterial filter. In some examples, a fully functional pump subassemblyincludes a titanium sleeve which comprises the pump bore, spring recess,valve seat and valve fastening features integrated with electromagneticdrive coil components. A titanium weld ring is integrated toelectromagnetic drive coil components to facilitate hermeticallyattaching pump components. A fully functional pump subassembly mayinclude a bacterial filter with a cover including stroke settingfeatures. Stroke setting feature integrated to cover that encloses thepumping actuator can provide a hermetic flow path of subassembly. Inaddition, a fully functional pump subassembly can include a valveassembly housed within the titanium sleeve. A “sandwich weld” can beused to permanently and hermetically weld the electromagnetic drive coilcomponents to the pump enclosure component by sealing the titanium weldring, a barrier plate over the drive coil and the cover with a singleweld. Some examples included in this disclosure can provide for testingpumping functionality (seal testing, electrical testing and mechanicalpump operation testing) of the pump subassembly as a standalonecomponent, i.e., without installing the pump subassembly within thecommon pump framework. As referred to herein, mechanical testingincludes testing the mechanical operation of the pump piston and or pumpvalve and electrical testing includes testing the functionality and/orintegrity of the pump coil. Seal testing includes looking for defects orleaks in welds and/or other seals of a pump or pump subassembly. Theseand other examples are described with respect to the figures included inthis disclosure.

FIG. 1 is a conceptual diagram illustrating an example of a therapysystem 10 including IMD 12, which is configured to deliver at least onetherapeutic agent, such as a pharmaceutical agent, insulin, painrelieving agent, anti-inflammatory agent, gene therapy agent, or thelike, to a target site within patient 16 via catheter 18, which iscoupled to IMD 12. In one example, catheter 18 may comprise a pluralityof catheter segments. In other examples, catheter 18 may be a unitarycatheter. In the example shown in FIG. 1, the target site is proximateto spinal cord 14 of patient 16. A proximal end 18A of catheter 18 iscoupled to IMD 12, while a distal end 18B of catheter 18 is locatedproximate to the target site. Therapy system 10 also includes externalprogrammer 20, which wirelessly communicates with IMD 12 as needed, suchas to provide or retrieve therapy information or control aspects oftherapy delivery (e.g., modify the therapy parameters, turn IMD 12 on oroff, and so forth). While patient 16 is generally referred to as a humanpatient, other mammalian or non-mammalian patients are alsocontemplated.

Generally, IMD 12 has an outer housing that is constructed of abiocompatible material that resists corrosion and degradation frombodily fluids, such as titanium or biologically inert polymers. IMD 12may be implanted within a subcutaneous pocket close to the therapydelivery site. For example, in the example shown in FIG. 1, IMD 12 isimplanted within an abdomen of patient 16. In other examples, IMD 12 maybe implanted within other suitable sites within patient 16, which maydepend, for example, on the target site within patient 16 for thedelivery of the therapeutic agent.

In accordance with the techniques described herein, IMD 12 includes amodular medical pump. A modular medical pump is a medical pump thatfacilitates assembly of at least a portion of the pump componentsseparately from the pump housing (or bulkhead) of IMD 12 containing afluid a fluid reservoir, a port and a medical pump subassembly. An IMDwith a modular medical pump may have a lower production cost compared toan IMD in which all or substantially all of the medical pump assemblyoccurs in conjunction with a bulkhead.

Catheter 18 may be coupled to IMD 12 either directly or with the aid ofa catheter extension (not shown in FIG. 1). In the example shown in FIG.1, catheter 18 traverses from the implant site of IMD 12 to one or moretarget sites proximate to spine 14. Catheter 18 is positioned such thatone or more fluid delivery outlets of catheter 18 are proximate to theone or more target sites within patient 16. IMD 12 delivers atherapeutic agent to the one or more target sites proximate to spinalcord 14 with the aid of catheter 18. IMD 12 can be configured forintrathecal drug delivery into the intrathecal space, as well asepidural delivery into the epidural space, both of which surround spinalcord 14. The epidural space (also known as “extradural space” or“peridural space”) is the space within the spinal canal (formed by thesurrounding vertebrae) lying outside the dura mater, which encloses thearachnoid mater, subarachnoid space, the cerebrospinal fluid, and spinalcord 14. The intrathecal space is within the subarachnoid space ofspinal cord 14, which is past the epidural space and dura mater andthrough the theca of spinal cord 14.

As already mentioned, in some applications, therapy system 10 can beused to reduce pain experienced by patient 16. In such an application,IMD 12 can deliver one or more therapeutic agents to patient 16according to one or more dosing programs that set forth differenttherapy parameters, such as a therapy schedule specifying programmeddoses, dose rates for the programmed doses, and specific times todeliver the programmed doses. The dosing programs may be a part of aprogram group for therapy, where the group includes a plurality ofdosing programs and/or therapy schedules. In some examples, IMD 12 maybe configured to deliver a therapeutic agent to patient 16 according todifferent therapy schedules on a selective basis. IMD 12 may include amemory to store one or more therapy programs, instructions defining theextent to which patient 16 may adjust therapy parameters, switch betweendosing programs, or undertake other therapy adjustments. Patient 16 or aclinician may select and/or generate additional dosing programs for useby IMD 12 via external programmer 20 at any time during therapy or asdesignated by the clinician.

In some examples, multiple catheters 18 may be coupled to IMD 12 totarget the same or different tissue or nerve sites within patient 16.Thus, although a single catheter 18 is shown in FIG. 1, in otherexamples, system 10 may include multiple catheters or catheter 18 maydefine multiple lumens for delivering different therapeutic agents topatient 16 or for delivering a therapeutic agent to different tissuesites within patient 16. Accordingly, in some examples, IMD 12 mayinclude a plurality of reservoirs for storing more than one type oftherapeutic agent. In some examples, IMD 12 may include a single longtube that contains the therapeutic agent in place of a reservoir.However, for ease of description, an IMD 12 including a single reservoiris primarily discussed herein with reference to the example of FIG. 1.

Programmer 20 is an external computing device that is configured towirelessly communicate with IMD 12. For example, programmer 20 may be aclinician programmer that the clinician uses to communicate with IMD 12.Alternatively, programmer 20 may be a patient programmer that allowspatient 16 to view and modify therapy parameters. The clinicianprogrammer may include additional or alternative programming features,relative to the patient programmer. For example, more complex orsensitive tasks may only be allowed by the clinician programmer toprevent patient 16 from making undesired changes to the operation of IMD12.

Programmer 20 may be a hand-held computing device that includes adisplay viewable by the user and a user input mechanism that can be usedto provide input to programmer 20. For example, programmer 20 mayinclude a display screen (e.g., a liquid crystal display or a lightemitting diode display) that presents information to the user. Inaddition, programmer 20 may include a keypad, buttons, a peripheralpointing device, touch screen, voice recognition, or another inputmechanism that allows the user to navigate though the user interface ofprogrammer 20 and provide input.

If programmer 20 includes buttons and a keypad, the buttons may bededicated to performing a certain function, i.e., a power button, or thebuttons and the keypad may be soft keys that change in functiondepending upon the section of the user interface currently viewed by theuser. Alternatively, the screen (not shown) of programmer 20 may be atouch screen that allows the user to provide input directly to the userinterface shown on the display. The user may use a stylus or theirfinger to provide input to the display.

In other examples, rather than being a handheld computing device or adedicated computing device, programmer 20 may be a larger workstation ora separate application within another multi-function device. Forexample, the multi-function device may be a cellular phone, personalcomputer, laptop, workstation computer, or personal digital assistantthat can be configured to an application to simulate programmer 20.Alternatively, a notebook computer, tablet computer, or other personalcomputer may execute an application to function as programmer 20, e.g.,with a wireless adapter connected to the personal computer forcommunicating with IMD 12.

When programmer 20 is configured for use by the clinician, programmer 20may be used to transmit initial programming information to IMD 12. Thisinitial information may include hardware information for system 10 suchas the type of catheter 18, the position of catheter 18 within patient16, the type and amount, e.g., by volume of therapeutic agent(s)delivered by IMD 12, a refill interval for the therapeutic agent(s), abaseline orientation of at least a portion of IMD 12 relative to areference point, therapy parameters of therapy programs stored withinIMD 12 or within programmer 20, and any other information the cliniciandesires to program into IMD 12. In accordance with some examples of thisdisclosure, the refill interval may be based on an expiration time forthe therapeutic agent(s).

The clinician uses programmer 20 to program IMD 12 with one or moretherapy programs that define the therapy delivered by IMD 12. During aprogramming session, the clinician may determine one or more dosingprograms that may provide effective therapy to patient 16. Patient 16may provide feedback to the clinician as to the efficacy of a specificprogram being evaluated or desired modifications to the dosing program.Once the clinician has identified one or more programs that may bebeneficial to patient 16, patient 16 may continue the evaluation processand determine which dosing program or therapy schedule best alleviatesthe condition of patient 16 or otherwise provides efficacious therapy topatient 16.

The dosing program information may set forth therapy parameters, such asdifferent predetermined dosages of the therapeutic agent (e.g., a doseamount), the rate of delivery of the therapeutic agent (e.g., rate ofdelivery of the fluid), the maximum acceptable dose, a time intervalbetween successive supplemental boluses such as patient-initiatedboluses (e.g., a lock-out interval), a maximum dose that may bedelivered over a given time interval, and so forth. IMD 12 may include afeature that prevents dosing the therapeutic agent in a mannerinconsistent with the dosing program. Programmer 20 may assist theclinician in the creation/identification of dosing programs by providinga methodical system of identifying potentially beneficial therapyparameters.

A dosage of a therapeutic agent, such as a drug, may be expressed as anamount of drug, e.g., measured in milligrams, provided to the patientover a particular time interval, e.g., per day or twenty-four hourperiod. This dosage amount may convey to the caregiver an indication ofthe probable efficacy of the drug and the possibility of side effects ofthe drug. In general, a sufficient amount of the drug should beadministered in order to have a desired therapeutic effect, such as painrelief. However, the amount of the drug administered to the patientshould be limited to a maximum amount, such as a maximum daily dose, inorder not to avoid potential side effects. Program information specifiedby a user via programmer 20 may be used to control dosage amount, dosagerate, dosage time, maximum dose for a given time interval (e.g., daily),or other parameters associated with delivery of a drug or other fluid byIMD 12. Dosage may also prescribe particular concentrations of activeingredients in the therapeutic agent delivered by IMD 12 to patient 16.

In some cases, programmer 20 may also be configured for use by patient16. When configured as the patient programmer, programmer 20 may havelimited functionality in order to prevent patient 16 from alteringcritical functions or applications that may be detrimental to patient16. In this manner, programmer 20 may only allow patient 16 to adjustcertain therapy parameters or set an available range for a particulartherapy parameter. In some cases, a patient programmer may permit thepatient to control IMD 12 to deliver a supplemental, patient bolus, ifpermitted by the applicable therapy program administered by the IMD,e.g., if delivery of a patient bolus would not violate a lockoutinterval or maximum dosage limit. Programmer 20 may also provide anindication to patient 16 when therapy is being delivered or when IMD 12needs to be refilled or when the power source within programmer 20 orIMD 12 need to be replaced or recharged.

Whether programmer 20 is configured for clinician or patient use,programmer 20 may communicate to IMD 12 or any other computing devicevia wireless communication. Programmer 20, for example, may communicatevia wireless communication with IMD 12 using radio frequency (RF)telemetry techniques known in the art. Programmer 20 may alsocommunicate with another programmer or computing device via a wired orwireless connection using any of a variety of local wirelesscommunication techniques, such as RF communication according to the802.11 or Bluetooth specification sets, infrared (IR) communicationaccording to the IRDA specification set, or other standard orproprietary telemetry protocols. Programmer 20 may also communicate withanother programming or computing device via exchange of removable media,such as magnetic or optical disks, or memory cards or sticks. Further,programmer 20 may communicate with IMD 12 and another programmer viaremote telemetry techniques known in the art, communicating via a localarea network (LAN), wide area network (WAN), public switched telephonenetwork (PSTN), or cellular telephone network, for example.

In other applications of therapy system 10, the target therapy deliverysite within patient 16 may be a location proximate to sacral nerves(e.g., the S2, S3, or S4 sacral nerves) in patient 16 or any othersuitable nerve, organ, muscle or muscle group in patient 16, which maybe selected based on, for example, a patient condition. For example,therapy system 10 may be used to deliver a therapeutic agent to tissueproximate to a pudendal nerve, a perineal nerve or other areas of thenervous system, in which cases, catheter 18 would be implanted andsubstantially fixed proximate to the respective nerve. As furtherexamples, catheter 18 may be positioned to deliver a therapeutic agentto help manage peripheral neuropathy or post-operative pain mitigation,ilioinguinal nerve therapy, intercostal nerve therapy, gastricstimulation for the treatment of gastric motility disorders and/orobesity, muscle stimulation, for mitigation of other peripheral andlocalized pain (e.g., leg pain or back pain). As another example,catheter 18 may be positioned to deliver a therapeutic agent to a deepbrain site or within the heart (e.g., intraventricular delivery of theagent). Delivery of a therapeutic agent within the brain may help manageany number of disorders or diseases. Example disorders may includedepression or other mood disorders, dementia, obsessive-compulsivedisorder, migraines, obesity, and movement disorders, such asParkinson's disease, spasticity, and epilepsy. Catheter 18 may also bepositioned to deliver insulin to a patient with diabetes.

Examples of therapeutic agents that IMD 12 may be configured to deliverinclude, but are not limited to, insulin, morphine, hydromorphone,bupivacaine, clonidine, other analgesics, genetic agents, antibiotics,nutritional fluids, analgesics, hormones or hormonal drugs, gene therapydrugs, anticoagulants, cardiovascular medications or chemotherapeutics.

FIG. 2 is a functional block diagram illustrating components of anexample of IMD 12, which includes refill port 26, reservoir 30,processor 38, memory 40, telemetry module 42, power source 44, medicalpump 46, internal tubing 32, and catheter connection port 36. Asdiscussed in further detail below, medical pump 46 may facilitatemechanical, electrical and seal testing as a standalone component.Catheter connection port 36 is one example of a port for delivering atherapeutic fluid to a patient; in other examples, IMD 12 may deliver atherapeutic agent without a catheter. Medical pump 46 may be a mechanismthat delivers a therapeutic agent in some metered or other desired flowdosage to the therapy site within patient 16 from reservoir 30 via thecatheter 18. Refill port 26 may comprise a self-sealing injection port.The self-selaing injection port may include a self-sealing membrane toprevent loss of therapeutic agent delivered to reservoir 30 via refillport 26. After a delivery system, e.g., a hypodermic needle, penetratesthe membrane of refill port 26, the membrane may seal shut when theneedle is removed from refill port 26. Internal tubing 32 is a segmentof tubing that runs from reservoir 30, around or through medical pump 46to catheter connection port 36.

Processor 38 controls the operation of medical pump 46 with the aid ofinstructions associated with program information that is stored inmemory 40. For example, the instructions may define dosing programs thatspecify the amount of a therapeutic agent that is delivered to a targettissue site within patient 16 from reservoir 30 via catheter 18. Theinstructions may further specify the time at which the agent will bedelivered and the time interval over which the agent will be delivered.The amount of the agent and the time over which the agent will bedelivered are a function of the dosage rate at which the fluid isdelivered. In other examples, a quantity of the agent may be deliveredaccording to one or more physiological characteristics of a patient,e.g., physiological characteristics sensed by one or more sensors (notshown) implanted within a patient as part of therapy system 10 (FIG. 1).Components described as processors within IMD 12 and external programmer20 may each comprise one or more processors, such as one or moremicroprocessors, digital signal processors (DSPs), application specificintegrated circuits (ASICs), field programmable gate arrays (FPGAs),programmable logic circuitry, or the like, either alone or in anysuitable combination.

Memory 40 may include any volatile or non-volatile media, such as arandom access memory (RAM), read only memory (ROM), non-volatile RAM(NVRAM), electrically erasable programmable ROM (EEPROM), flash memory,and the like. As mentioned above, memory 40 may store programinformation including instructions for execution by processor 38, suchas, but not limited to, therapy programs, historical therapy programs,timing programs for delivery of fluid from reservoir 30 to catheter 18,and any other information regarding therapy of patient 16. Memory 40 mayinclude separate memories for storing instructions, patient information,therapy parameters (e.g., grouped into sets referred to as “dosingprograms”), therapy adjustment information, program histories, and othercategories of information such as any other data that may benefit fromseparate physical memory modules.

Telemetry module 42 in IMD 12, as well as telemetry modules in acontroller, such as programmer 20, may accomplish communication by RFcommunication techniques. In addition, telemetry module 42 maycommunicate with programmer 20 via proximal inductive interaction of IMD12 with external programmer 20. Processor 38 controls telemetry module42 to send and receive information.

Power source 44 delivers operating power to various components of IMD12. Power source 44 may include a small rechargeable or non-rechargeablebattery and a power generation circuit to produce the operating power.In the case of a rechargeable battery, recharging may be accomplishedthrough proximal inductive interaction between an external charger andan inductive charging coil within IMD 12. In some examples, powerrequirements may be small enough to allow IMD 12 to utilize patientmotion and implement a kinetic energy-scavenging device to tricklecharge a rechargeable battery. In other examples, traditional batteriesmay be used for a limited period of time. As a further alternative, anexternal inductive power supply could transcutaneously power IMD 12whenever measurements are needed or desired.

FIGS. 3-6 illustrate components of medical pump 100. For example,medical pump 100 may be part of an IMD, such as IMD 12 (FIG. 1). Medicalpump 100 includes modular pump coil subassembly 120, piston/polesubassembly 160, cover 170, bulkhead 180 and filter 190. In accordancewith the techniques described herein, the configuration of medical pump100 facilitates electrical and seal integrity testing of modular pumpcoil subassembly 120 as a standalone component, i.e., prior to assemblyof modular pump coil subassembly 120 within bulkhead 180.

As shown in FIG. 3, bulkhead 180 includes cup-mounting bay 182 toreceive modular pump coil subassembly 120 and filter-mounting bay 184 toreceive filter 190. Fluid passageway 186 connects cup-mounting bay 182to filter-mounting bay 184. Bulkhead 180 comprises a biocompatiblematerial. As examples, bulkhead 180 may include a stainless steel alloy,a titanium alloy or other biocompatible material.

During the operation of medical pump 100, therapeutic fluid flowsthrough filter 190 and into cup-mounting bay 182 via fluid passageway186. Within cup-mounting bay 182, the fluid enters an enclosureincluding piston/pole subassembly 160 through holes 174 in cover 170.Once within the enclosure under cover 170, the fluid enters centralaperture 150 and is pushed by the motion of piston 166 through one-wayvalve 152 (FIG. 4A). After passing through valve 152, the therapeuticfluid is directed to one or more target sites within a patient. Forexample, as shown in FIG. 1, a catheter may be used to directtherapeutic fluid from a medical pump to a target site within a patient.

Filter 190 includes three elements: filter cover 194, filter element 192and filter base 196. Base 196 forms a seal with filter-mounting bay 184to prevent any therapeutic fluid from bypassing filter element 192 priorto entering fluid passageway 186. Filter cover 194 serves to compressfilter element 192 and base 196 to provide a seal between filter element192 and base 196 as well as a seal between base 196 and bulkhead 180.Filter cover 194 may be attached to bulkhead 180 by interference fit,screws (not shown) or other suitable techniques. Each of the elements offilter 190 comprise corrosion-resistant materials. As an example, base196 may comprise a deformable material, such as a polymer or siliconerubber. In other examples, base 196 may comprise a stainless steel orother suitable material. As another example, cover 194 may comprise apolymer, a stainless steel or other suitable material.

Pump coil subassembly 120 operates to drive piston/pole subassembly 160during a pump stroke of medical pump 100. The components of modular pumpcoil subassembly 120 are shown in FIGS. 4A-4B. Pump coil subassembly 120includes cup assembly 140, electromagnetic coil 134, barrier plate 130and one-way valve 152. Electromagnetic coil 134 fits underneath barrierplate 130 and within recess 149 of cup assembly 140. In addition,one-way valve 152 seals against seat 151 within the end of sleeve 144 ofcup assembly 140 opposite barrier plate 130.

As shown in FIG. 5, cup assembly 140 includes magnetic cup 141, weldring 146 and sleeve 144. Magnetic cup 141 forms recess 149. Withinrecess 149, magnetic cup 141 includes protrusion 145. In addition,magnetic cup 141 forms central aperture 150 in protrusion 145, whichreceives sleeve 144. As an example, sleeve 144 may be interference fitwithin central aperture 150 or secured within central aperture 150 byother techniques. Weld ring 146 surrounds recess 149 and fits withingroove 143 of magnetic cup 141. Weld ring 146 may be interference fit togroove 143 of magnetic cup 141 or secured by other techniques. Magneticcup 141 comprises a highly magnetic material. The highly magneticmaterial of magnetic cup 141 efficiently magnetizes in response tocurrent through electromagnetic coil 134. As an example, magnetic cup141 may comprise a highly magnetic steel alloy. As another example,magnetic cup 141 may comprise a highly magnetic stainless steel alloysuch as 430F. However, as highly magnetic materials are generallysusceptible to corrosion, magnetic cup 141 is separated from the flowpath of fluid being pumped by medical pump 100 to prevent corrosion ofmagnetic cup 141. As will be discussed in greater detail, weld ring 146combines with bulkhead 180, barrier plate 130 and sleeve 144 to separatemagnetic cup 141 from the flow path.

Electromagnetic coil 134 comprises one or more insulated conductorsarranged in a multitude of turns. As examples, electromagnetic coil 134may comprise a single continuous conductor or more than one conductorelectrically connected in series or in parallel. Electromagnetic coil134 includes flex circuit 136, which provides the electrical connectionsused to deliver current to electromagnetic coil 134. Within medical pump100, delivering current to electromagnetic coil 134 magnetizes magneticcup 141 in order to attract pole 162 for a pump stroke of medical pump100. Flex circuit 136 fits through hole 142 of magnetic cup 141 and alsothrough hole 183. Hole 183 is formed in the bottom of cup-mounting bay182 in bulkhead 180 and lines up with hole 142 to receive flex circuit136.

Barrier plate 130 covers recess 149 to enclose electromagnetic coil 134within recess 149. Barrier plate 130 forms mating aperture 131, whichprovides an inner diameter of barrier plate 130. Mating aperture 131coincides with central aperture 150 of magnetic cup 141. The innerdiameter of barrier plate 130 is sealed to sleeve 144, whereas the outerdiameter of barrier plate 130 is sealed to weld ring 146. For thisreason, the inner diameter of barrier plate 130 may be smaller than theinner diameter of magnetic cup 141, but larger than the inner diameterof sleeve 144. Barrier plate 130 comprises a relatively thin material toprovide the best magnetic performance for pump 100 while maintainingsufficient strength and stiffness to isolate electromagnetic coil 134and magnetic cup 141 from the flow path. For example, barrier plate 130may have a thickness between about 0.0005 inches to about 0.10 inches.As other examples, barrier plate 130 may have a thickness between about0.001 inches to about 0.010 inches, a thickness between about 0.001inches to about 0.005 inches, a thickness of less than about 0.010inches, a thickness of less than about 0.005 inches, a thickness betweenabout 0.00175 inches to about 0.00225 inches, or a thickness of about0.002 inches. Barrier plate 130 comprises a biocompatible material. Asexamples, barrier plate 130 may include a stainless steel alloy, atitanium alloy or other biocompatible material.

Piston/pole subassembly 160 includes piston 166 and pole 162.Piston/pole subassembly 160 is positioned such that piston 166 islocated within central aperture 150 of modular pump coil subassembly120. Spring 132 is located within central aperture 150 adjacent distalend 167 of piston 166. Spring 132 functions to bias piston/polesubassembly 160 away from modular pump coil subassembly 120 such thatpole 162 is spaced apart from barrier plate 130. Piston 166 may beinterference fit to pole 162 or secured to pole 162 by other suitabletechniques. Pole 162 comprises a magnetic material that is attracted tocup assembly 140 to produce a pump stroke. As an example, pole 162 maycomprise a stainless steel. Between holes 174 formed in cover 170 andcentral aperture 150, therapeutic fluid flows through holes 168 in pole166 as well as through a gap between pole 162 and inner surface ofsidewall 176 of cover 170. Because pole 162 is within the fluid flowpath, the material of pole 162 should resist corrosion. As an example,pole 162 may comprise a magnetic stainless steel alloy, such as AL29-4.Likewise, piston 166 is also located within the fluid flow path andshould also resist corrosion. As an example, piston 166 may comprisesapphire material, which can limit wear between piston and sleeve 144caused by the pumping action of medical pump 100. As other examples,piston 166 may comprise a metal material, such as a stainless steel ortitanium alloy. In some examples, piston/pole subassembly 160 maycomprises a unitary component consisting of a single magnetic materialsuch as a stainless steel alloy.

Cover 170 mounts to barrier plate 130 to form an enclosure containingpiston/pole subassembly 160 and spring 132. When medical pump 100 isfully-assembled, cover 170 is secured to bulkhead 180 withincup-mounting bay 182. As examples, cover 170 may be interference fitwithin cup-mounting bay 182 or secured to bulkhead 180 using a weldjoint, one or more screws or other techniques. Cover 170 includes holes174, which allow the therapeutic fluid passing through medical pump 100to enter the enclosure formed by cover 170 after passing through fluidpassageway 186. Cover 170 also includes protrusions 172, which arelocated on its interior surface adjacent to pole 162. Protrusions 172serve constrain the motion of piston/pole subassembly 160 therebylimiting the maximum stroke length of a pump stoke. In this manner, theheight of protrusion s 172 may be selected to set the stroke length of apump stroke. As the volume of therapeutic fluid delivered by medicalpump 100 per pump stroke directly (pump-stroke volume) relates to thestroke length, the design of medical pump 100 facilitates differentpump-stroke volumes simply by changing the height of protrusions 172.The other components of medical pump 100 can be identical for differentpump-stroke volumes. However, the pump-stroke volume also depends on thediameter of piston 166 and the inner diameter of sleeve 144, and canalso be selected in combination with a stroke length to provide selectedpump-stroke volumes.

Piston/pole subassembly 160 actuates within an enclosure between aninterior surface of cover 170 and an exterior surface of barrier plate130. Spring 132 biases piston/pole subassembly 160 away from valve 152and against protrusions 172 of cover 170. The motion of piston/polesubassembly 160 is driven by electromagnetic coil 134. Specifically,during a pump stroke, current through electromagnetic coil 134 serves tomagnetize magnetic cup 141 to attract pole 162. The magnetic attractionforce between pole 162 and magnetic cup 141 overcomes the force ofspring 132 to create a pumping action of piston 166. The motion ofpiston 166 forces therapeutic fluid within central aperture 150 andadjacent to distal end 167 of piston 166 through one-way valve 152.

Following a pump stroke, current through electromagnetic coil 134 stops,and spring 132 returns piston/pole subassembly 160 to its originalposition against cover 170. As spring 132 moves piston/pole subassembly160, therapeutic fluid flows through a small gap between piston 166 andthe inner surface of sleeve 144 to fill the growing space within centralaperture 150 adjacent to distal end 167 of piston 166. While sometherapeutic fluid could technically flow back though the gap betweenpiston 166 and the inner surface of sleeve 144 during a pump stroke, thespeed of a pump stroke combined with the viscosity of the therapeuticfluid allows any amount of therapeutic fluid flowing back though the gapbetween piston 166 and the inner surface of sleeve 144 during a pumpstroke to be negligible.

The size of the gap between piston 166 and the inner surface of sleeve144 may be selected according to the fluid being pumped through medicalpump 100. For example, a higher viscosity fluid may take more time thana lower viscosity fluid to flow through gap between piston 166 and theinner surface of sleeve 144 for a given gap and a given spring forcefrom spring 132. The size of the gap as well as the spring force fromspring 132 may be selected to limit backflow during a pump stroke aswell as provide a return stroke fast enough for a desired pump strokerate according to the fluid properties of a particular therapeutic to bepumped through medical pump 100. Generally the gap between piston 166and the inner surface of sleeve 144 should be selected to preventbackflow while spring 132 should provide a near minimal spring forcenecessary to accomplish a return stroke fast enough to provide a desiredpump stroke rate. These are examples of how medical pump 100 can becustomized to suit a particular application with limited modification.

Generally, a return stroke is relatively slow compared to a pump stroke.As an example, a pump stoke may take about 0.01 to 100 milliseconds,whereas a return stroke may take about 0.5 to 20 seconds. As anotherexample, a pump stoke may take about 1 to 10 milliseconds, whereas areturn stroke may take about 0.1 to 20 seconds. As another example, apump stoke may take about 1 to 5 milliseconds, whereas a return strokemay take about 0.5 to 5 seconds. As yet another example, a pump stokemay take about 3 milliseconds, whereas a return stroke may take about 2seconds. In this manner, the configuration of piston 166 and sleeve 144acts as a one-way valve during the operation of medical pump 100.

Therapeutic fluid pushed by piston 166 during a pump stroke exitsmedical pump 100 through one-way valve 152. One-way valve 152 includesthree components: disc 154, spring 156 and bonnet 158. Spring 156functions to bias disc 154 against seat 151 of sleeve 144. Bonnet 158functions to hold spring 156 in place. As an example, bonnet 158 may beinterference fit to sleeve 144. In other examples, bonnet 158 may beattached to sleeve 144 using a weld joint, screws or by other suitabletechniques. In yet other examples, valve 152 may be located remotely. Insuch examples, a sealed fluid passageway, such as a catheter, wouldconnect sleeve 144 and valve 152. Bonnet 158 includes holes that providefluid passageways through bonnet 158. When one-way valve 152 is closed,disc 154 seals to seat 151 of sleeve 144. The configuration of one-wayvalve 152 may be referred to as a lift check valve. In other examples,different valve configurations may be used including, but not limitedto, ball check valves, diaphragm valves, gate valves and other valves.The design of medical pump 100 allows different valves to be selectedfor one-way valve 152 as desired according to a particular therapeuticto be pumped through medical pump 100 and the desired pumpingcharacteristics. Generally, one-way valve 152 should be selected tominimize a pressure differential in the fluid flow path at one-way valve152 while maintaining a fluid seal except during pump strokes.

As best shown in FIG. 6, magnetic cup 141 is separated from the flowpath of fluid being pumped by medical pump 100. In the manufacture ofmodular pump coil subassembly 120, the outer diameter of barrier plate130 is sealed to weld ring 146 to enclose electromagnetic coil 134within recess 149. In addition, the interior diameter of barrier plate130 is sealed to sleeve 144. As shown in FIG. 6, barrier plate 130 issealed to sleeve 144 with a first weld joint, i.e., weld joint 122, andbarrier plate 130 is sealed to weld ring 146 with a second weld joint,i.e., weld joint 124. In other examples, barrier plate 130 may be sealedto weld ring 146 and sleeve 144 using other techniques. Weld ring 146forms notch 147, which is adjacent to an outer perimeter of barrierplate 130. Weld joint 124 is at least partially located within notch147. As an example, the external diameter of barrier plate 130 may besubstantially the same as the inner diameter of notch 147.

The combination of barrier plate 130, sleeve 144, weld ring 146 and weldjoints 122, 124 serves to fluidically separate an interior of magneticcup 141, from an external surface of barrier plate 130, i.e., thesurface opposite magnetic cup 141, and thus separate the interior ofmagnetic cup 141 from fluid being pumped through magnetic pump 100. Inaddition, modular pump coil subassembly 120 is installed within bulkhead180 such that weld ring 146 is sealed to cup-mounting bay 182 tofluidically separate an exterior of magnetic cup 141 from an externalsurface of barrier plate 130, and thus separate the exterior of magneticcup 141 from fluid being pumped through magnetic pump 100.

As examples, weld ring 146 may be interference fit within bulkhead 180within cup-mounting bay 182 or sealed to bulkhead 180 with a weld jointor other suitable techniques. In this manner, the design of medical pump100 completely separates magnetic cup 141 from fluid being pumpedthrough magnetic pump 100. This allows magnetic cup 141 to be formedfrom a highly magnetic material, such as a highly magnetic steel, whichmay have a low resistance to corrosion. In contrast, weld ring 146,sleeve 144, barrier plate 130 and bulkhead 180 comprise materials thatresist corrosion. Examples of suitable materials include stainless steeland titanium alloys.

The design of cup assembly 140 and, more specifically, weld ring 146,allows modular pump coil subassembly 120 to be assembled separately frombulkhead 180 and tested as a standalone component. In addition, thedesign of cup assembly 140, including weld ring 146, also allows testingthe integrity of seals at the inner and outer diameter of barrier plate130 before mounting modular pump coil subassembly 120 to bulkhead 180and electrical testing of electromagnetic coil 134. In one example of amanufacturing process of magnetic pump 100, the integrity of weld joints122, 124 is tested before potting coil 134 within cup assembly 140 toensure a tight seal at weld joints 122, 124. Potting involves encasingcoil 134 within a non-conductive material within recess 149 by pouring(or forcing) a non-conductive potting material though hole 139 (FIG. 4B)in magnetic cup 141 after barrier plate 130 is sealed to weld ring 146and sleeve 144. Because the seals separating the interior of magneticcup 141 from the external surface of barrier plate 130, i.e., weldjoints 122, 124 are part of cup assembly 140 and do not include bulkhead180, the design of modular pump coil subassembly 120 allows coil 134 tobe potted within cup assembly 140 before cup assembly 140 is mounted tobulkhead 180 within cup-mounting bay 182. The design of medical pump 100also allows electrical testing of electromagnetic coil 134 after pottingand before mounting modular pump coil subassembly 120 to bulkhead 180.

In general, potting includes allowing the potting material to “set-up”or harden after filling the remaining space within recess 149 within thepotting material. As examples, a potting material may be an epoxy or apolymer. Potting coil 134 within cup assembly 140 can take a significantamount of time to allow the potting material to harden. Depending on thepotting material, potting can take between about 1 to 24 hours. Asanother example, potting can take about between about 2 to 12 hours. Asanother example, potting can take about 8 hours. Because the pottingprocess takes a significant amount of time, separating potting processfrom bulkhead 180 streamlines the assembly of medical pump 100.

In addition, during the manufacturing of a plurality of medical pumps100, some of weld joints 122, 124 will not form proper seals. In suchinstances, the faulty cup assembly 140 may be removed from the assemblyprocess. In contrast, in an alternative design in which the outerdiameter of barrier plate 130 is sealed directly to cup-mounting bay 182of bulkhead 180, e.g., using a weld joint, instead of indirectly viaweld ring 146, testing the integrity of the seal between barrier plate130 and cup-mounting bay 182 could only be performed after mountingmagnetic cup 141 within cup-mounting bay 182. In such an alternativedesign, in the event of a bad seal, the entire assembly, includingbulkhead 180, would have to be removed from the assembly process. Inthis manner, the design of medical pump 100 provides the advantage offacilitating a manufacturing process that does not waste a bulkhead 180in the event of a bad seal at one of weld joints 122, 124.

While numerous techniques may be suitable to manufacture cup assembly140, the following techniques may be included in the manufacture cupassembly 140. In each stage of the following description, components arereferred to using the same names as these components have in afull-assembled medical pump 100, even though such components may not yetinclude each its associated features provided during the previousdescription of medical pump 100.

Central aperture 150 is machined in magnetic cup 141 to receive sleeve144; likewise, sleeve 144 is bored to accept piston 166. Next, sleeve144 is interference fit within central aperture 150 of magnetic cup 141.Then, valve seat 151 is finish-machined to accept valve 152, and thebore of sleeve 144 is also finish-machined to piston 166. Following thisstep, the combined magnetic cup 141/sleeve 144 is passivated using acidand vacuum-baked. Vacuum-baking may limit the occurrence of corrosion atthe interface between magnetic cup 141 and sleeve 144 and the interfacebetween magnetic cup 141 and weld ring 146 during future heat treatmentprocesses. For example, such corrosion may be caused by particles leftbehind by tooling used in the finish machining. Following thevacuum-baking, the combined magnetic cup 141/sleeve 144 is heat treated.The heat treatment forms a hard titanium-oxide layer on sleeve 144,which improves the wear resistance of sleeve 144 to limit wear caused bythe motion of piston 166.

Next, groove 143 is machined in magnetic cup 141, and weld ring 146 ismachined from a titanium alloy to fit groove 143. Weld ring 146 is theninterference fit within groove 143 of magnetic cup 141. Then, cupassembly 140 is finished-machined. Finish machining including machiningnotch 147 in weld ring 146 as well as forming recess 149 within magneticcup 141. Forming recess 149 within magnetic cup 141 includes leavingprotrusion 145 in place. The finish machining also includes facing-offthe upper surfaces of magnetic cup 141, including protrusion 145, sleeve144 and weld ring 146 to ensure these surfaces are substantiallycoplanar. It is useful to ensure that the upper surfaces of magnetic cup141 are substantially coplanar to improve the likelihood that weldjoints 122, 124 will form proper seals with barrier plate 130. Followingthis step, the cup assembly 140 is again passivated with acid andvacuum-baked. One-way valve 152 is then seated in valve seat 151 ofsleeve 144. The forgoing description provides an example of techniquesthat may be included in the manufacture cup assembly 140. Othertechniques and combinations of techniques may be used in the manufactureof cup assembly 140.

Modular pump coil subassembly 120 can be electrically and seal tested asa standalone component. This limits manufacturing costs by detectingdefective pump components before installation of pump coil subassembly120 within a bulkhead. In addition, modular pump coil subassembly 120allows for faster assembly because potting of the pump coil occurs priorto the assembly line process, further limiting manufacturing costs byreducing the time and space required for the assembly of an IMDincluding pump coil subassembly 120.

FIGS. 7-10 illustrate components of modular medical pump 200, inaccordance with another example. Medical pump 200 facilitates pumpoperation testing prior to assembling the modular medical pump in abulkhead, i.e., testing of modular pump 218 as a standalone component.Medical pump 200 includes modular pump 218 with cover 270, whichincludes filter element 276 (FIG. 9), and bulkhead 280. In manyrespects, medical pump 200 is similar to medical pump 100. For example,many of the components described with respect to medical pump 100 arealso suitable for medical pump 200. These components are numbered thesame in FIGS. 7-10 with respect to medical pump 200 as in FIGS. 3-6 withrespect to medical pump 100. For brevity, such components are describedin little, if any, detail with respect to medical pump 200.

Like medical pump 100, medical pump 200 may be part of an IMD, such asIMD 12 (FIG. 1). In contrast to medical pump 100, medical pump 200includes a modular pump, modular pump 218, which is mechanically andelectrically functional without bulkhead 280. Medical pump 200 alsoincludes bulkhead 280. Modular pump 218 includes cup assembly 140, coil134, barrier plate 130, spring 132, piston/pole subassembly 160, cover270 and one-way valve 152.

As shown in FIG. 7, bulkhead 280 includes cup-mounting bay 282 toreceive modular pump 218. In contrast to bulkhead 180 (FIG. 3), bulkhead280 does not include a filter-mounting bay. Instead, cover 270 ofmedical pump 200 includes an integrated filter. As with bulkhead 180,bulkhead 280 comprises a biocompatible material. As examples, bulkhead280 may include a stainless steel alloy, a titanium alloy or otherbiocompatible material.

As shown in FIG. 9, cover 270 includes perforated screen 274, filterelement 276, gasket 278 and base 279. Gasket 278 forms a seal betweenfilter element 276 and base 279 to prevent any therapeutic fluid flowingthrough modular pump 218 (FIG. 7) from bypassing filter element 276.Perforated screen 274 serves to compress filter element 276 and gasket278 to provide a seal between filter element 276 and gasket 278 as wellas a seal between gasket 278 and base 279. As the components of cover270 are within the flow path of fluid being pumped by medical pump 200,the components of cover 270 comprise biocompatible materials. Asexamples, perforated screen 274 and base 279 may comprise a stainlesssteel, titanium alloy or other suitable material. As another example,perforated screen 274 and base 279 may comprise a polymer, a stainlesssteel or other suitable material. In addition, gasket 278 may comprise adeformable material, such as a polymer, silicon rubber or other suitablematerial.

Holes 273 provide the fluid flow path through base 279. In addition,base 279 includes protrusion 272, which serves constrain the motion ofpiston/pole subassembly 160 thereby limiting the maximum stroke lengthof a pump stoke. As discussed with respect to protrusions 172 in medicalpump 100, the height of protrusion 272 may be selected to set the strokelength of a pump stroke of medical pump 200.

As best shown in FIG. 10, magnetic cup 141 is separated from the flowpath of fluid being pumped by medical pump 200. In the manufacture ofmodular pump 218, the interior diameter of barrier plate 130 is firstsealed to sleeve 144. Then, the outer diameter of barrier plate 130 issealed to weld ring 146 to enclose electromagnetic coil 134 withinrecess 149. As shown in FIG. 10, barrier plate 130 is sealed to sleeve144 with a first weld joint: weld joint 122, and barrier plate 130 issealed to weld ring 146 with a second weld joint: weld joint 224.However, in contrast to medical pump 100, the second weld joint, weldjoint 224 also attaches cover 270 to barrier plate 130 and weld ring146. Because cover 270 is placed over barrier plate 130 prior to formingweld joint 224, weld joint 224 can not interfere with the placement ofcover 270 against barrier plate 130. In contrast, in medical pump 100,weld joint 124 (FIG. 6) could potentially interfere with the placementof cover 270 against barrier plate 130. The location of cover 270 isimportant at least because protrusions 272 serve to set the strokelength of a pump stroke of medical pump 200.

Weld ring 146 forms notch 147, which is adjacent to an outer perimeterof barrier plate 130. Likewise, base 279 of cover 270 forms notch 281,which is adjacent to notch 147 in weld ring 146. Weld joint 224 ispartially located within notch 147, and weld joint 224 is also partiallylocated within notch 281. As an example, the external diameter ofbarrier plate 130 may be substantially the same as the inner diameter ofnotch 147 and the inner diameter of notch 281. The combination ofbarrier plate 130, sleeve 144, weld ring 146 and weld joints 122, 224serves to fluidically separate an interior of magnetic cup 141 from anexternal surface of barrier plate 130, and thus separate the interior ofmagnetic cup 141 from fluid being pumped through magnetic pump 200. Inaddition, modular pump 218 is installed within bulkhead 280 such thatweld ring 146 is sealed to cup-mounting bay 282 to fluidically separatean exterior of magnetic cup 141 from an external surface of barrierplate 130, and thus separate the exterior of magnetic cup 141 from fluidbeing pumped through magnetic pump 200. As examples, weld ring 146 maybe interference fit within bulkhead 280 within cup-mounting bay 282 orsealed to bulkhead 280 with a weld joint or other suitable techniques.In this manner, the design of medical pump 200 completely separatesmagnetic cup 141 from fluid being pumped through magnetic pump 200.

As discussed with respect to medical pump 100, the design of medicalpump 200 allows potting of coil 134 to be performed separately from theassembly of components to bulkhead 280, which streamlines themanufacture of medical pump 200. The design of medical pump 200 alsoallows seal integrity testing of weld joints 122, 224. Furthermore,modular pump 218 can be electrically, mechanically and seal tested as astandalone component, i.e., prior to installation in bulkhead 280. Thisadditional testing further ensures the functionality of the componentsof medical pump 200 prior to final assembly in bulkhead 280. Oneadditional advantage of the design of medical pump 200 as compared tomedical pump 100 is that a higher class cleanroom, i.e., a dirtiercleanroom, may be used during the assembly processes including bulkhead280. For example, assembly of medical pump 100 and modular pump 218 maybe performed in an International Organization for Standardization (ISO)14644-1 Class 5 (FED STD 209E Class 100) cleanroom, whereas assembly ofmedical pump 200 may be performed in an ISO 14644-1 Class 7 (FED STD209E Class 10,000) cleanroom.

FIGS. 11-12B illustrate components of modular medical pump 300. Medicalpump 300 is substantially similar to medical pump 200, with theexception that cover 370 does not include an integrated filter element.The design of medical pump 300 facilitates pump operation testing of themodular medical pump as a standalone component, i.e., prior toassembling the modular medical pump in a bulkhead. Medical pump 300includes cover 370, filter element 190 and bulkhead 380. In manyrespects, medical pump 300 is similar to medical pumps 100, 200. Forexample, many of the components described with respect to medical pumps100, 200 are also suitable for medical pump 300. For brevity, suchcomponents are described in little, if any, detail with respect tomedical pump 300.

Medical pump 300 may be part of an IMD, such as IMD 12 (FIG. 1). Medicalpump 300 includes modular pump 318, filter element 190 and bulkhead 380.Modular pump 318 includes cup assembly 140, coil 134, barrier plate 130,spring 132, piston/pole subassembly 160, cover 370 and one-way valve152.

As shown in FIG. 11, bulkhead 380 includes cup-mounting bay 382 toreceive modular pump 318 and filter-mounting bay 384 to receive filter190. Fluid passageway 386 connects cup-mounting bay 382 tofilter-mounting bay 384. Bulkhead 380 comprises a biocompatiblematerial. As examples, bulkhead 380 may include a stainless steel alloy,a titanium alloy or other biocompatible material. Cover 370 alsocomprises a biocompatible material such as a stainless steel, titaniumalloy or other suitable material.

In contrast to cover 270 of modular pump 218, cover 370 is a unitarycomponent. Fluid passageway 374 in cover 370 directs fluid from fluidpassageway 386 in bulkhead 380 into modular pump 318. Cover 370 includesprotrusion 372, which serves to constrain the motion of piston/polesubassembly 160 thereby limiting the maximum stroke length of a pumpstoke. As discussed with respect to protrusions 172 in medical pump 100,the height of protrusion 372 may be selected to set the stroke length ofa pump stroke of medical pump 300. Cover 370 also forms notch 381, whichis adjacent to notch 147 in weld ring 146. A weld joint sealing weldring 146, the outer diameter of barrier plate 130, and cover 370 ispartially located within notch 147 and also partially located withinnotch 381. As an example, the external diameter of barrier plate 130 maybe substantially the same as the inner diameter of notch 147 and theinner diameter of notch 381.

As discussed with respect to medical pump 100, the design of medicalpump 300 allows potting of coil 134 to be performed separately from theassembly of components to bulkhead 380, which streamlines the assemblyof medical pump 300. The design of medical pump 300 also allows sealintegrity testing and electrical and mechanical testing of pump 300 as astandalone component. This testing further ensures the functionality ofthe components of medical pump 300 prior to final assembly in bulkhead380. In addition, as discussed with respect to medical pump 200, ahigher class clean room, i.e., dirtier, may be used during assemblyprocesses including bulkhead 380 than for assembly of modular pump 318.

FIG. 13 is a flowchart illustrating techniques for manufacturing amedical pump. For clarity, the techniques shown in FIG. 13 are describedwith respect to medical pump 100. Some of the assembly steps may beautomated whereas other steps may be performed manually. First, magneticcup 141 and weld ring 146 are assembled (402). For example, weld ring146 may be assembled to magnetic cup 141 by interference fit. Next,electromagnetic coil 134 is placed within recess 149 circumscribingprotrusion 145 (404). Barrier plate 130 is then sealed to weld ring 146to enclose the electromagnetic coil 134 within recess 149 (406), andintegrity of the seals of barrier plate 130 is tested (408). Sealingbarrier plate 130 to weld ring 146 and to sleeve 144 fluidicallyseparates an interior of magnetic cup 141 from an external surface ofbarrier plate 130. Next, electromagnetic coil 134 is potted withinmagnetic cup recess 149 (410). Finally, modular pump coil subassembly120 is placed within cup-mounting bay 182 of bulkhead 180 (412) and weldring 146 is sealed to bulkhead 180 (414) to fluidically separate anexterior of magnetic cup 141 from an external surface of barrier plate131.

FIG. 14 is a flowchart illustrating techniques for manufacturing amedical pump including a pump module. For clarity, the techniques shownin FIG. 14 are described with respect to medical pump 200. First,magnetic cup 141 and weld ring 146 are assembled (422). For example,weld ring 146 may be assembled to magnetic cup 141 by interference fit.Next, electromagnetic coil 134 is placed within recess 149circumscribing protrusion 145 (424). The inner diameter of barrier plate130 is then sealed to sleeve 144 of cup assembly 140, e.g., with weldjoint 122 (426). Spring 132 and piston 166 of piston/pole subassembly160 are positioned within central aperture 150 (428). Cover 270 ispositioned over barrier plate 130 and piston/pole subassembly 160. Theouter diameter of barrier plate 130 is then sealed to weld ring 146 andcover 270 with weld joint 224 (430), and integrity of the seals ofbarrier plate 130 is tested (432). In other examples, such as medicalpump 500 in FIG. 16, two separate weld joints 523, 524 may be used toseal the outer diameter of a barrier plate 130 to a weld ring 146 and acover 570 (430). Sealing barrier plate 130 to weld ring 146 and tosleeve 144 fluidically separates an interior of magnetic cup 141 from anexternal surface of barrier plate 130. Next, electromagnetic coil 134 ispotted within recess 149 (434). Optionally, modular pump 218 may then beelectrically, mechanically and seal tested as a standalone component.Finally, modular pump 218 is mounted with cup-mounting bay 282 ofbulkhead 280 (436), and weld ring 146 is sealed to bulkhead 180 tofluidically separate an exterior of magnetic cup 141 from an externalsurface of barrier plate 131.

Medical pumps designs having a fixed stroke length, such as medicalpumps 100, 200, 300 may be easier to manufacture and more reliable thanmedical pumps with adjustable stroke lengths. As referred to herein,medical pumps having a fixed stroke length, is a medical pump in whichthe stroke length of a piston of the pump is not adjustable in a mannerthat could account for variability in the manufacture of a plurality ofsubstantially identical medical pumps, e.g., a series of medical pumpsmanufactured according to the same design and specifications. However,in contrast to medical pumps with adjustable stroke lengths, individualmedical pumps with fixed stroke lengths can not be calibrated to accountfor variability in the manufacturing process to ensure that each of aplurality of substantially identical pumps provide the same volume offluid delivered per pump stroke. As referred to in this disclosure,pumps are considered to be substantially identical pumps if builtaccording to the same design and specifications, such as a series ofpumps manufactured using interchangeable parts on the same assemblyline. In some medical pump applications, such as the delivery oftherapeutic fluids, the variability in volume of fluid delivered perpump stroke among a plurality of substantially identical pumps is notprecise enough to provide optimal patient treatment using the medicalpumps. For this reason, it may be useful to calibrate a patient therapyprogram to a measured volume of fluid delivered per pump stroke for themedical pump in a plurality of substantially identical pumps beingcontrolled by the patient therapy program. In other words, a patienttherapy program may be slightly adjusted to deliver desired therapywhile compensating for slight differences between differentsubstantially identical pumps.

FIG. 15 is a flowchart illustrating techniques for delivering specifiedquantities of therapeutic fluid to patients using medical pumps withfixed stroke lengths. For clarity, the techniques shown in FIG. 15 aredescribed with respect to IMD 12, programmer 20 and medical pumps 100,200, 300.

First, following the manufacture or assembly of a plurality of medicalpumps having fixed stroke lengths, a volume of fluid delivered per pumpstroke is measured for each of the medical pumps (440). Medical pumps100, 200, 300 are examples of medical pumps with fixed stroke lengths.In addition, pump modules 218, 318 are also considered medical pumpswith fixed stroke lengths as pump modules 218, 318 provide the pumpingfunction of medical pumps 200, 300. Measuring a volume of fluiddelivered per pump stroke in a medical pump may include connecting themedical pump to a power source, pumping a fluid with the medical pumpusing a known number of pumping strokes, and measuring (e.g., by mass orvolume) the pumped fluid to determine the volume of fluid delivered perpump stroke of the medical pump. The volume of fluid delivered may bemeasure automatically as part of the assembly process, or manually,either as part of the assembly process, or by a clinician prior tooperation of a medical pump in conjunction with a patient.

Indications of the measured volumes are stored in memory (442). Anindication of a measured volume could be entered manually, e.g., into auser-interface of programmer 20 or automatically by an instrument usedto measure the volumes. As examples, the memory could be included in anIMD including the medical pump, such as memory 40 in IMD 12. As anotherexample, the memory could be a memory of a programmer such as programmer20.

As other examples, the memory could be a removable data storage media,such as a compact disc, memory card, magnetic disk, or the like. In somecases, the information may be stored as part of a computer database thatincludes indications of volumes of fluid delivered per pump stroke forplurality of substantially identical medical pumps. The storedindication of volume of fluid per pump stroke for a medical pump isstored in a manner that associates the medical pump with the storedindication. For example, the indication may be stored in a memoryassociated with the medical pump and/or the indication may be storedwith a unique identifier, e.g., a serial number, of the medical pump toassociate the medical pump with the stored indication.

Following implantation of an IMD including the medical pump in apatient, the stored indication of volume of fluid delivered can be usedto calibrate a therapy program for the delivery of a therapeutic fluidto the patient. For example, for each medical pump, a programmer, suchas programmer 20, may receive an indication of a specified quantity oftherapeutic fluid to be delivered to a patient from a user (444). Indifferent examples, the user may be the patient or a clinician. Thespecified quantity of therapeutic fluid may be defined as a volume, as aflow-fate, according to one or more physiological characteristics of thepatient or by other means.

Next, for each medical pump, a processor accesses the indication ofvolume of fluid per pump stroke for a medical pump stored in memory andgenerates a therapy program based on the indication of volume of fluiddelivered per pump stroke and the specified quantity of therapeuticfluid to be delivered to the patient (446). The processor can be locatedin an IMD including the medical pump, within a programmer associatedwith the medical pump or within a remote device in communication withtherapy system 10.

As an example, the processor may be processor 38 of IMD 12. In such anexample, IMD 12 may receive the specified quantity of therapeutic fluidto be delivered to the patient from programmer 20 and generate thetherapy program based on the indication of volume of fluid per pumpstroke automatically. Such a process may occur automatically and withoutthe knowledge of a user who provided the specified quantity of fluid tobe delivered.

As another example, the processor may be part of controller 20. In suchan example, controller 20 may then issue instructions to IMD 12 todeliver the therapeutic fluid with the equivalent quantity of pumpstrokes rather than directly specifying a quantity of fluid delivered inthe instructions to IMD 12. Again, such a process may occurautomatically and without the knowledge of a user who provided thespecified quantity of fluid to be delivered.

After generation of the therapy programs, each of the medical pumpsdeliver a specified quantity of therapeutic fluid to a patient using atherapy program calibrated to that particular medical pump based on avolume of fluid delivered per pump stroke measured from that particularmedical pump (448).

In the manner, the specified quantities of therapeutic fluid to bedelivered are converted to equivalent quantities of pump strokes basedon indications of the volume of fluid delivered per pump stroke storedin a memory to account for variability in the manufacture of a pluralityof substantially identical medical pumps. Generally, the techniques ofFIG. 15 are repeated for each of the plurality of substantiallyidentical medical pumps.

FIG. 16 illustrates components of modular medical pump 500, inaccordance with another example. Medical pump 500 facilitates pumpoperation testing of modular medical pump 518 as a standalone component,i.e., prior to assembly of modular medical pump 518 in bulkhead 280.Like medical pump 200, medical pump 500 may be part of an IMD, such asIMD 12 (FIG. 1). Medical pump 500 includes modular pump 518 and bulkhead280. Modular pump 518 includes cup assembly 140, coil 134, barrier plate530, spring 132, piston/pole subassembly 160, cover 570 and one-wayvalve 152.

Medical pump 500 is substantially similar to medical pump 200. Oneexception is that the functionality of weld joints 523, 524 in medicalpump 200 is provided by two separate weld joints 523, 524 in medicalpump 500. In addition, barrier plate 530 has a smaller outer diameterthan barrier plate 530 to accommodate weld joint 523, and base 579 ofcover 570 includes notch 583 to accommodate weld joint 523.

Cover 570 includes perforated screen 274, filter element 276, gasket 578and base 579. Gasket 578 forms a seal between filter element 276 andbase 579 to prevent any therapeutic fluid flowing through modular pump518 from bypassing filter element 276. Perforated screen 274 serves tocompress filter element 276 and gasket 578 to provide a seal betweenfilter element 276 and gasket 578 as well as a seal between gasket 578and base 579. As the components of cover 570 are within the flow path offluid being pumped by medical pump 200, the components of cover 570comprise biocompatible materials. As examples, perforated screen 274 andbase 579 may comprise a stainless steel, titanium alloy or othersuitable material. As another example, perforated screen 274 and base579 may comprise a polymer, a stainless steel or other suitablematerial. In addition, gasket 578 may comprise a deformable material,such as a polymer, silicon rubber or other suitable material. Gasket 578has a round cross-section, which in contrast to gasket 278 of cover 270,which has a rectangular cross-section. However, gasket 278 and gasket578 provide equivalent functionality.

Holes 573 provide the fluid flow path through base 579. In addition,base 579 includes protrusion 572, which serves constrain the motion ofpiston/pole subassembly 160 thereby limiting the maximum stroke lengthof a pump stoke. As discussed with respect to protrusions 172 in medicalpump 100, the height of protrusion 572 may be selected to set the strokelength of a pump stroke of medical pump 200.

Magnetic cup 141 is separated from the flow path of fluid being pumpedby medical pump 500. In the manufacture of modular pump 518, theinterior diameter of barrier plate 530 is first sealed to sleeve 144with weld joint 122 and the outer diameter of barrier plate 530 issealed to weld ring 146 with weld joint 523 to enclose electromagneticcoil 134 within recess 149. Then, in contrast to medical pump 200, athird weld joint, weld joint 524, attaches cover 570 to barrier plate530 and weld ring 146. In this manner, the thickness of barrier plate530 does not influence the height of protrusion 572 relative to magneticcup 141 and weld ring 146.

Weld ring 146 forms notch 147, which is adjacent to an outer perimeterof cover 570. Likewise, base 579 of cover 570 forms notch 581, which isadjacent to notch 147 in weld ring 146. Weld joint 524 is partiallylocated within notch 147, and weld joint 524 is also partially locatedwithin notch 581. In addition, base 579 also forms notch 583 at theinner diameter of base 579. Notch 583 is adjacent to the externaldiameter of barrier plate 530. Weld joint 523 is partially locatedwithin notch 583.

The combination of barrier plate 530, sleeve 144, weld ring 146 and weldjoints 122, 523, 524 serve to fluidically separate an interior ofmagnetic cup 141 from an external surface of barrier plate 530, and thusseparate the interior of magnetic cup 141 from fluid being pumpedthrough magnetic pump 500. In addition, modular pump 518 is installedwithin bulkhead 280 such that weld ring 146 is sealed to cup-mountingbay 282 to fluidically separate an exterior of magnetic cup 141 from anexternal surface of barrier plate 530, and thus separate the exterior ofmagnetic cup 141 from fluid being pumped through magnetic pump 500. Asexamples, weld ring 146 may be interference fit within bulkhead 280within cup-mounting bay 282 or sealed to bulkhead 280 with a weld jointor other suitable techniques. In this manner, the design of medical pump500 completely separates magnetic cup 141 from fluid being pumpedthrough magnetic pump 500.

The techniques described in this disclosure may be implemented, at leastin part, in hardware, software, firmware or any combination thereof. Forexample, various aspects of the described techniques may be implementedwithin one or more processors, including one or more microprocessors,digital signal processors (DSPs), application specific integratedcircuits (ASICs), field programmable gate arrays (FPGAs), or any otherequivalent integrated or discrete logic circuitry, as well as anycombinations of such components. The term “processor” or “processingcircuitry” may generally refer to any of the foregoing logic circuitry,alone or in combination with other logic circuitry, or any otherequivalent circuitry. A control unit comprising hardware may alsoperform one or more of the techniques of this disclosure.

Such hardware, software, and firmware may be implemented within the samedevice or within separate devices to support the various operations andfunctions described in this disclosure. In addition, any of thedescribed units, modules or components may be implemented together orseparately as discrete but interoperable logic devices. Depiction ofdifferent features as modules or units is intended to highlightdifferent functional aspects and does not necessarily imply that suchmodules or units must be realized by separate hardware or softwarecomponents. Rather, functionality associated with one or more modules orunits may be performed by separate hardware or software components, orintegrated within common or separate hardware or software components.

The techniques described in this disclosure may also be embodied orencoded in a computer-readable medium, such as a computer-readablestorage medium, containing instructions. Instructions embedded orencoded in a computer-readable medium may cause a programmableprocessor, or other processor, to perform the method, e.g., when theinstructions are executed. Computer-readable storage media may includerandom access memory (RAM), read only memory (ROM), programmable readonly memory (PROM), erasable programmable read only memory (EPROM),electronically erasable programmable read only memory (EEPROM), flashmemory, a hard disk, a CD-ROM, a floppy disk, a cassette, magneticmedia, optical media, or other computer readable media.

Various examples of the disclosure have been described. However,modifications to the described examples may be made within the spirit ofthe disclosure. As an example, the described examples generally referredto medical pumps as delivering a therapeutic fluid to a target sitewithin a patient. However, medical pumps may also be used to removefluid from a patient. Specific examples of draining include usingmedical pumps to drain cerebrospinal fluid (CSF) from a patient andusing medical pumps to drain other fluids from a cavity within apatient. These and other examples are within the scope of the followingclaims.

The invention claimed is:
 1. An assembly comprising: a medical pumpsubassembly, the medical pump subassembly comprising: a magnetic cupforming a recess, wherein the magnetic cup includes a protrusion withinthe recess, wherein the cup forms a central aperture through theprotrusion, an electromagnetic coil within the recess and circumscribingthe protrusion, a weld ring surrounding the recess, a barrier platecovering the recess, a sleeve within the central aperture, wherein thesleeve forms a bore configured to receive a piston, wherein the barrierplate forms a mating aperture that coincides with the central apertureof the cup, a first seal between the weld ring and the barrier plate,and a second seal between the sleeve and the barrier plate, wherein thefirst seal and the second seal combine to fluidically separate aninterior of the cup from an external surface of the barrier plate; abulkhead including a bay, wherein the medical pump subassembly ismounted within the bay; and a third seal between the cup and thebulkhead to fluidically separate an exterior of the cup from an externalsurface of the barrier plate.
 2. The assembly of claim 1, furthercomprising a potting material encasing the electromagnetic coil withinthe recess.
 3. The assembly of claim, wherein the first seal is a firstweld joint, and wherein the second seal is a second weld joint.
 4. Theassembly of claim 3, wherein the sleeve is interference fit in thecentral aperture of the cup.
 5. The assembly of claim 3, furthercomprising a one-way valve in the sleeve opposite to the barrier plate.6. The assembly of claim 1, wherein the cup forms a groove surroundingthe recess, and wherein the weld ring is interference fit in the groove.7. The assembly of claim 1, further comprising a one-way valve in thecentral aperture opposite to the barrier plate.
 8. The assembly of claim1, wherein the weld ring includes a notch adjacent to an outer perimeterof the barrier plate, wherein the seal is a weld joint between thebarrier plate and the weld ring, and wherein the weld joint is at leastpartially located within the notch.
 9. The assembly of claim 1, whereinthe weld ring comprises titanium.
 10. The assembly of claim 1, whereinthe magnetic cup comprises a highly magnetic material, and wherein theweld ring, the barrier plate, and the sleeve each comprise biocompatiblemetal materials.
 11. A medical pump assembly comprising: a magnetic cupforming a recess, wherein the magnetic cup includes a protrusion withinthe recess, wherein the cup forms a central aperture through theprotrusion; a one-way valve that controls fluid flow within the centralaperture; an electromagnetic coil within the recess and circumscribingthe protrusion; a barrier plate covering the recess; a piston within thecentral aperture; a magnetic pole attached to the piston, wherein themagnetic pole is adjacent to an external surface of the barrier plate; acover enclosing the magnetic pole between an interior surface of thecover and an external surface of the barrier plate, wherein the coverconstrains the motion of the piston within the central aperture; and aseal between the cup and the barrier plate and the cover to fluidicallyseparate an interior of the cup from the external surface of the barrierplate.
 12. The medical pump assembly of claim 11, wherein the sealincludes a weld joint between the cup, the barrier plate and the cover.13. The medical pump assembly of claim 12, wherein the seal is a firstseal, the assembly further comprising: a sleeve within the centralaperture, wherein the barrier plate forms a mating aperture thatcoincides with the central aperture of the cup; and a second sealbetween the sleeve and the barrier plate to fluidically separate theinterior of the cup from the external surface of the barrier plate. 14.The medical pump assembly of claim 11, wherein the cup comprises a weldring surrounding the recess, wherein the seal is between the weld ringand the barrier plate.
 15. The medical pump assembly of claim 14,wherein the weld ring includes a first notch adjacent to an outerperimeter of the barrier plate, wherein the cover includes a secondnotch adjacent to the first notch, wherein the seal is a weld jointbetween the cup, the barrier plate and the cover, and wherein the weldjoint is at least partially located within both the first notch and thesecond notch.
 16. The medical pump assembly of claim 11, furthercomprising: a bulkhead including a cup-mounting bay, wherein the cup ismounted within the bay; and a second seal between the cup and thebulkhead to fluidically separate an exterior of the cup from an externalsurface of the barrier plate.
 17. The medical pump assembly of claim 11,wherein the cover includes a filter within an inlet flow path of themedical pump assembly.
 18. The medical pump assembly of claim 11,wherein the cover includes one or more protrusions on the interiorsurface of the cover, wherein the protrusions define a stroke length ofthe piston.
 19. The medical pump assembly of claim 11, wherein the coverlimits a stroke length of the piston, and wherein the cover is a unitaryelement such that the cover limits the stroke length of the piston as anon-adjustable fixed length.